Fumigation of plants with ozone in the field is most
frequently carried out using open-top chambers (OTCs).

A great majority of the data used in developing the
exposure-response relationships was obtained using (OTCs).

Charcoal- and particulate-filtered air, non-filtered
air, or ozone-supplemented air is blown into the bottom layer,
forced through the perforations into the plant canopy, and then
allowed to escape through the top of the chamber.

The OTC exposure system was employed in the National
Crop Loss Assessment Network (NCLAN) program from 1980 to 1988.

Plants grown in open-top chambers usually use different
treatment levels, where

Plants are exposed to
air in chambers that attempt to take most of the ozone out of
the chamber (carbon-filtered);

Plants are exposed to
air in chambers that are at ambient levels (non-filtered); and

Plants are exposed to
air in chambers where ozone is added at multiple levels (e.g.,
2X).

Variable growth or injury
responses are obtained when the biological endpoints are compared
among different chamber treatments.